Sealed Zinc-nickel Battery Additives And Anode Materials For The Preparation And Performance

This paper briefly reviews the history and current situation of Ni-Zn battery, and focus on the research progress of secondary Ni-Zn battery, including its working principle, existed problems and the corresponding solutions, and then the application prospects of Ni-Zn battery was expected. Constant current charge-discharge tests, SEM and hydrogen evolution experiment were used to study the effects of dispersant on the electrochemical performance of Ni-Zn battery. Effect of zinc oxide with different morphology on Ni-Zn battery was investigated, and the matching technology of anode and cathode electrode were groped. The calcium zincate synthesized by ball milling was characterized by XRD and SEM. The difference of electrochemical performance of various calcium zincate was studied by constant current charge-discharge tests and anatomical analysis of batteries. In addition, the self-discharge performance of Ni-Zn battery was investigated by changing separators, shell and electrolyte as well as additives in cathode.The study of various dispersants in zinc electrode shows that addition of sodium hexametaphosphate, sodium tripolyphosphate, ethanol and Tween-20 in the paste of zinc electrode can prevent zinc active materials from agglomerating and affect the electrochemical performance of batteries. Especially, the addition of sodium hexametaphosphate improved the electrochemical performance most greatly. The SEM result and hydrogen evolution experiments indicated that the sodium hexametaphosphate prevented ZnO and graphite from agglomerating greatly and suppressed the hydrogen evolution of zinc electrode.The effects of ZnO with different morphology on zinc electrode were compared. The results show that the ordinary ZnO has higher specific capacity (303 rnAh·g^-1), higher discharge capacity and charge-discharge efficiency and longer cycle life than the nanosized ZnO (237 mAh·g^-1). It was found that the discharge capacity of Ni-Zn battery was not only limited by the capacity of nickel electrode but also the activity of ZnO. When the capacity of zinc electrode is 1.7 times of that of nickel electrode and keep the 90% depth of charge capacity, the Ni-Zn battery have both better electrochemical performance and active material utilization.Irregular calcium zincate was synthesized by ball milling method in different concentrations of KOH solution. The obtained samples were verified by XRD and SEM. The results showed that the structure of calcium zincate changed from CaZn₂(OH)₆·2H₂O into Ca(Zn(OH)₃)₂·2H2O as the concentration of KOH increasing, and the calcium zincate would not be synthesized when the concentration of KOH is over 40%. The constant current charge/discharge tests of battery indicated that calcium zincate synthesized in 20% KOH solution has better charge/discharge performance and capacity. In addition, effects of morphology of calcium zincate on high-rate charge/discharge performance of zinc electrode were mainly investigated by constant current charge/discharge tests. The results show that there was little difference in low-rate charge/discharge ratio, but the difference was significant as the ratio increasing. The negative with regular calcium zincate, especially the hexangular calcium zincate has better high-rate charge/discharge performance than the irregular one.Sulfonated separators can restrain the self-discharge of Ni-Zn battery more effectively than the vinylon separators because of it's stability in high alkalescence and high temperature. The EIS tests indicate that charge transfer resistance of both the cathode and anode increased greatly by using NaOH electrolyte instead of KOH electrolyte in Ni-Zn battery. After stored for 30 days at room temperature, the capacity retention rate with 1C rate increased from 13.3% to 28.3%, especially in 6 M NaOH, the capacity retention rate was 32.2%. The Ca(OH)₂ and MnO₂ added in nickel electrodes improved the overpotential of oxygen evolution and restrained the self decomposition of anode, and thus both of the self-discharge and the storage performance were enhanced. The various coating of Sn or Cu on battery shell restrained the hydrogen evolution effectively after stored for 7 days at 50℃, the capacity retention rate with 1C rate were 35.6% and 24.7%, while on the coating of Ni is 0.